What is an arguido?

An "arguido" - normally translated as "named suspect" or "formal suspect" - is someone who is treated by Portuguese police as more than a witness, but has not been arrested or charged.

Under Portuguese law, a person declared an arguido - "arguida" in the case of a woman - has legal protection that is not extended to a witness, including the right to remain silent during questioning and the right to legal representation.

Detectives invoke arguido status on someone as a preliminary to an arrest being made or charges brought, a Portuguese law expert, Lita Gale, told Guardian Unlimited today.

"If you are an arguido they have to have suspicion that a crime has been committed by that person," she said.

She added that when someone's status moves from that of a witness to an arguido, the police interview technique changes.

"Depending on the answers they may be moving towards a prosecution. If you cannot provide an alibi or the right answers they may move to prosecute. This is a serious moment. The suspect may be close to being charged," Ms Gale said.

Technically, police should treat someone as an arguido as soon as they have sufficient evidence. However, in some circumstances they may hold back to give somebody "a false sense of security", she added.

In practical terms, a person has to be declared an arguido before he or she can be arrested. Police may also ask a local court to place restrictions on a person's movement and oblige them to not leave the country.

Once a case file is completed, the police pass it to the public ministry, the equivalent of the crown prosecution service, which decides whether an "acusacao" or indictment is brought.

Portuguese authorities express caution against expecting that arrests or charges will automatically follow.

It is not uncommon for people caught up in criminal investigations in Portugal to declare themselves arguidos in order to receive more legal protection, particularly if they feel the line of questioning implies they are a suspect.

The ex-pat Briton, Robert Murat, was declared an arguido in the Madeleine case in May but has not been charged or formally arrested.